Auxiliary heaters are known and have been arranged in seats or outside mirrors of automotive vehicles. However, they are utilized most frequently in or on rear windows. In all cases, the problem exists of increasing operating convenience, while yet adapting the heating efficiency as optimally as possible to requirements for the auxiliary heater. Furthermore, too vigorous a heating action by the auxiliary heater is to be avoided in view of total energy balance and fuel consumption.
The timed starting of a window heater is shown by German Pat. No. 668,916. It is also shown by German Auslegeschrift 2,751,563 to control the rear window heater by a switching unit for a wiper and rinse system of the rear window. However, any kind of adaptation of the rear window heater to the internal and external conditions, e.g., the internal and external temperatures of the vehicle cannot be attained thereby. German Pat. No. 2,654,357 discloses activation of the rear window heater by a switch for a heater blower. None of these prior teachings suggest the conrol of an auxiliary heater in a manner and for the reasons as taught by the instant invention.